Most people today are involved in a sport or some other type of physical activity. Some of these activities involve a low risk chance of injury, such as walking and swimming, while others involve a high risk chance of injury, such as football and skiing.
Damaged ligaments, cartilage and tendons in joints are not an uncommon occurrence, particularly in some of these high risk activities and sports. One of the joints which requires particular skill and presents particular difficulties in repairing is the knee joint.
Numerous improvements in repairing damage to knee joints have been made over the years, and some of the major advances involve the use of endoscopic techniques and arthroscopic procedures. Arthroscopic surgery is particularly useful in excising or repairing damaged knee cartilage.
Endoscopic techniques have also been developed for use in repair and reconstruction of damaged anterior cruciate ligaments (ACL) and posterior cruciate ligaments (PCL). When the ACL in particular has ruptured and is nonrepairable, it is usually replaced in young adults and the knee reconstructed through use of grafts (biological or synthetic). Some known methods and techniques which have been used to repair and replace ACL ruptures with grafts are discussed, for example, in Moore U.S. Pat. No. 4,773,417, Goble U.S. Pat. No. 4,772,286 and an article by Goble entitled "FLUOROARTHROSCOPIC ALLOGRAFT ANTERIOR CRUCIATE RECONSTRUCTION", Techniques Orthop. 1988 2(4):65-73.
The function of the real cruciate ligaments is complicated. The ACL and PCL are three-dimensional structures with broad attachments and a continuum of fibers. These fibers are of different lengths, have different attachment sites, and are under different tensions. Although many current substitutes for cruciate ligaments have not duplicated the complex orientation and operation of normal ACLs, they operate the best and mimic the normal ACL operation the best when they are placed isometrically. "Isometrically" positioned means that the length of the substitute ligament will not change during angular movement of the tibia relative to the femur; the distance between the affixed ends of the ligament remains a constant. Isometric placement maximizes the number of fibers that can be taut throughout the range of motion of the knee and allows for early knee motion without generating high ligament strains.
Correct isometric positioning of the ACL graft is an important factor for a successful operation; isometrically placed grafts provide the most stable knees. Correct isometric placement reproduces corresponding femoral and tibial anatomic attachment sites and will allow an ACL graft to mimic the normal ACL. Non-isometric graft placement can result in plastic deformation of the ACL substitute, postoperative laxity, abnormal kinematics, or failure of fixation.
The importance of accurate placement of the graft tunnels and ACL substitute is shown by the fact that graft placements sometimes only several millimeters apart produce significantly different strains in the cruciate substitute. A placement of the ACL origin or insertion which is too anteriorly placed in the knee joint results in a ligament that is taut in flexion, but lax in extension. Posterior placement causes the ligament to be taut in extension, but lax in flexion. Only isometric tunnel placement provides stability throughout the range of motion. Therefore, one of the challenges during anterior cruciate ligament replacement procedures is the accurate isometric placement of the tibial tunnel.
The preparation of the intercondylar notch is also important as is the proper positioning and placement of the femoral and tibial tunnels. Accurate and sufficient notchplasty prevents impingement of the graft which could cause failure or significant complications. Often today the amount and degree of notchplasty is determined during an operation by "feel" or experience. This frequently results in more of the bone in the notch being removed than is necessary, or in less of the bone being removed than is required necessitating later correction in the operation.
U.S. Pat. No. 5,300,077 to Howell, the inventor herein, discloses methods and instruments for ACL reconstruction. Many of the method steps disclosed therein for replacement of an ACL are substantially utilized herein. However, the drill guide and method for using according to the present invention represent improvements in that portion of the procedure surrounding the formation of the tibial tunnel for an ACL graft.
Additionally, reconstructed knees typically regain more extension, have less pain and exhibit better stability when anterior cruciate ligament grafts are placed without femoral roof impingement. This is true, at least in part, because impingement of an ACL upon the femoral roof causes flexion contractures because the graft constrains the knee as a mechanical stop. If abrasion progresses to involve all the fibers of the graft, then the graft can fail, resulting in recurrent instability of the knee. To avoid flexion contractures and recurrent instability caused by roof impingement, the tibial tunnel should be positioned posterior and parallel to the slope of the intercondylar roof with the knee in full extension.
Another related challenge in the ACL replacement procedure is to minimize the amount of bone removed from the femoral intercondylar roof to prevent impingement during extension. Correct placement of the tibial tunnel prevents abrasive wear between the ACL graft and the intercondylar roof while minimizing the extent of roofplasty required to avoid impingement. This results in time and effort savings, and maximizes the desirable feature of preserving the maximum amount of natural bone in the knee. It is another goal of ACL replacement procedures to create tibial tunnel placement that may allow the implanted ACL to interact more normally with the PCL.
Standard tibial drill guides place the tibial tunnel in the same relative position for each patient. The most favorable position is often determined using these devices with reference to a single point on one of the bone surfaces in the knee joint region. This single reference point may be a tibial surface such as the PCL, the ACL stump or another point of reference. The determination of a favorable tunnel position may also involve the use of pins or other ancillary guide devices used in connection with the main device used for guiding the procedure. The use of such additional devices may cause these procedures to be more time-consuming and involve a greater amount of effort on the part of the surgeon. They may also require a greater number of surgical incisions for their insertion, and/or may require the use of two hands or more than one person for their manipulation.
In practice, however, different patients have different anatomies pertinent to formation of the tibial tunnel. The differences in these anatomies often occur in more than a one-dimensional context. For example, the degree of knee extension and the slope of the femoral intercondylar roof vary widely between knees. Therefore, the optimum location for the tibial tunnel, with regard to isometry, minimizing impingement and allowing proper interaction with the PCL may vary among patients in more than a one-dimensional context. Because use of a single reference point places the tibial tunnel at the same relative location for each patient, a multiple reference point system that takes several surfaces into account can provide superior determination of the optimum tibial tunnel location.
It is an object of the present invention to provide an improved method using endoscopic/arthroscopic techniques for reconstruction of ACLs. It is a further object to provide isometric placements of ACL substitutes, and isometric placements which are objectively accurate and reproducible.
It is also an object of the invention to insure against impingement of the ACL substitute/graft in the joint. It is another object of the invention to provide a system for accurately determining whether notchplasty needs to be performed in the intercondylar notch to prevent impingement, and then performing the necessary notchplasty.
It is still a further object of the invention to provide an ACL replacement which is minimally invasive in order to minimize trauma and facilitate faster patient healing and rehabilitation. It is another object to provide a method of ACL reconstruction which preferably uses biological grafts from the patient.
Further objects of the invention include development and use of improved instruments for ACL operations which help assure accurate and sufficient notchplasty of the intercondylar notch, and provide an improved method for ACL reconstruction.
It is therefore advantageous to develop an instrument for ACL replacement procedures, and a method for using, that determines custom placement of the tibial graft tunnel, for maximizing isometry, minimizing graft impingement and allowing proper ACL-PCL interaction. It is also advantageous to develop an instrument that is convenient and quick to use, that minimizes effort required by the surgeon and reduces the number of ancillary devices required.